Search

The article discusses a study which investigates the chemical composition and bioactivities of Euonymus acanthocarpus collected from Xishuangbanna, in Yunnan Province, China in August 2010. The study involves the extraction of 95% ethanol from the stems and leaves of E. acanthocarpus. Four terpenes, four aryl glycosides, seven flavones, and twenty aromatic compounds were isolated from the said plant.

The article presents a study which examined the chemical composition of the perennial herb Inula hookeri collected from Weixi county, Yunnan Province, China in August 2010. The compounds from the herbs which were extracted, isolated and purified using silica gel, column chromatography (CC) yielded colorless and yellow oils, gums, amorphous powder and crystals.

The lake state and chemistry are sensitive to climate change at short timescales, but it is unclear how lake hydrochemistry responds to monsoonal climate, especially over glacial-interglacial cycles, owing to lack of well-dated and continuous sedimentary records. The types and geochemical compositions of authigenic carbonates from lacustrine sediments can be used to reconstruct past hydrochemistry. Yet, little is known about the significance and influencing factors of the Mg/Ca and Sr/Ca ratios of authigenic carbonates over glacial-interglacial cycles. Here, trace-element data of a 666 m long sediment sequence from the Heqing basin, a paleo-lake situated at the southeastern margin of the Tibetan Plateau, provide detailed glacial-interglacial hydrochemical conditions and their association with Indian summer monsoon (ISM) evolution during the entire Pleistocene. In interglacials, variation in both Mg/Ca and Sr/Ca ratios can serve as proxies for salinity as a result of precipitation of low-Mg calcite, constrained by enhanced ISM intensity and catchment weathering product. Instead, in glacials, high Mg/Ca and Sr/Ca ratios reflect high-Mg calcite and aragonite precipitation under low lake level conditions. There is a nonlinear response of the Sr/Ca ratio of lacustrine sediment to salinity variation when high-Mg calcite and aragonite precipitate in a hydrologically closed and evaporative lake. Based upon the sedimentary Sr/Ca and Mg/Ca ratios in the Heqing paleo-lake, the lake hydrochemistry during the Pleistocene experienced obvious glacial-interglacial ISM cycles at the life span of the lake itself: (1) in the old interval (2640–1840 ka), the salinity was low with cycles at the early stage of lake development owing to strong ISM; (2) in the middle interval (1840–920 ka), the lake was at a balance state and its salinity was more constrained by weathering solute, rather than ISM; and (3) in the young interval (920–130 ka), the salinity fluctuated with large amplitude over glacial-interglacial cycles and subsequent increase paced the weakened ISM. This study highlights the sensitivity of the types of lacustrine authigenic carbonates and lake chemistry to ISM changes over glacial-interglacial cycles. • In the monsoon-impacted areas, sedimentary Mg/Ca and Sr/Ca ratios controlled by ISM intensity and catchment weathering. • Mg/Ca ratios of lacustrine sediment reflect the types of authigenic carbonates over glacial-interglacial cycles. • Sr/Ca ratios of lacustrine sediment record salinity linearly in the interglacials, but nonlinearly in the glacials • Through time, lake hydrochemistry response to catchment weathering gradually decreased. [ABSTRACT FROM AUTHOR]

Silicate weathering via CO 2 consumption is considered to regulate the long-term climate change. Discriminating silicate versus carbonate weathering from sedimentary records is helpful to understand the coupling relationship between weathering and past climate. However, owing to the paucity of well-dated and continuous records of weathering and erosion, the relationship between silicate and carbonate weathering and their links with mountain uplift and glacial-interglacial climate remain elusive. Geochemical analysis of a 666 m core from the Heqing basin, a paleolake situated at the southeastern margin of the Tibetan Plateau, demonstrates silicate versus carbonate weathering and erosion changes under Indian summer monsoon (ISM) conditions spanning the entire Pleistocene, via respective tracing between Rb/Sr and Al/Na ratios. The Rb/Sr record is interpreted as reflecting a competition between clayey silicate-origin Rb versus carbonate-origin Sr fluxes, whereas Al/Na ratio is a balance between weathering and erosion of silicate minerals, both pacing the glacial-interglacial cycles of the ISM. During interglacials, strong silicate weathering intensity reflected by low Al/Na values is mainly controlled by warmer temperatures, with the reduced variability during 1.82–0.92 Ma, recalling the pacing of the Arabian Sea surface temperature amplitudes. Within glacials, the weak carbonate leaching and clay erosion within the older and younger intervals are interrupted by strong clay erosion within the middle interval. In conclusion, the Heqing Rb/Sr and Al/Na records reveal the sensitivity of catchment weathering and erosion to ISM changes over glacial-interglacial timescales with warmer temperature enhancing silicate weathering and clay formation during interglacials and greater physical erosion during glacials. • Weathering and erosion history under the Indian summer monsoon (ISM) spanning the entire Pleistocene is provided. • Both silicate and carbonate weathering pace the ISM over glacial-interglacial timescales. • During interglacials, silicate weathering intensity is mainly controlled by temperature. • During glacials, carbonate leaching and clay erosion dominate. [ABSTRACT FROM AUTHOR]